Neutron spectroscopy
Neutron spectroscopy probes the dynamics of magnetic moments, molecules and lattices over length scales ranging from a few angstroms to tens of nanometers, and over timescales from tens of femtoseconds up to the microsecond. Within neutron spectroscopy, there are 4 main techniques which use different methods to determine the energy of the incident and scattered neutrons and are adapted to different kinds of scientific studies.
Dynamic ranges
Various dynamic ranges of the Spin-echo, Back-scattering and Time-of-flight instruments at the ILL. Figure made by M. Appel.
Time-of-flight spectrometry
There are 3 dedicated time-of-flight (TOF) spectrometers (IN5, SHARP+ and PANTHER) which use the time-of-flight of neutrons through the spectrometer to determine the energies of the incident and scattered neutrons. The instruments are optimized for different kinds of scientific studies, which depends mainly on their energy resolution and momentum transfer range.
An overview of instrument parameters is provided in the table below to help you choose the most suitable instrument. By clicking on the instrument, you can go directly to the dedicated instrument pages where more information can be found, including scientific highlights and contact details for the instrument scientists.
Time-of-flight instrument parameters
| IN5 | SHARP+ | PANTHER | |
|---|---|---|---|
| λ (Å) | 15 to 1.5 | 6 to 1.5 | 3.3 to 0.79 |
| Incoming energy Ei (meV) | 0.36 to 36 | 2.2 to 36.4 | 7.5 to 130 |
| energy resolution ΔE (meV) | 4 µeV to 2.7 meV | 0.055 to 3.0 | |
| Energy resolution ΔE / Ei | 7 to 1 % | 2.5 to 15.0 % | 3.8 to 5.5 % |
| Max energy transfer in % of Ei | 70 % | 45 % | 85 % |
| Qmin (A-1) | 0.5/λ | 0.4/λ | 0.06√ Ei |
| Qmax (A-1) | 11.6/λ | 11.8/λ | 1.28√ Ei |
| Horizontal dectector angles (deg) | 5 to 135 | 0 to 140 | 5 to 136 |
| Vertical detector angles (deg) | -20.5 to 20.5 | -22 to 22 | -13 to 30 |
Vibratrional spectrometrer
Vibrational instrument parameters
| IN1-LAGRANGE | ||
|---|---|---|
| λ (Å) | 0.4 | 4.26 |
| energy resolution (meV) | 2-3 % of Ei | |
| incident energy (meV) | ||
| energy transfer (meV) | 0-500 | |
| Qmin (A-1) | 0,86 (reached at Ei=4,5meV) | |
| Qmax (A-1) | 15 (at Ei=500meV) | |
| Detector definition angle minimum - maximum | ||
| Comments | Scanning instrument, so the incident wavelength can be changed from 0,4 up to 4,26 | |
Triple-axis spectrometry
There is a range of triple-axis (TAS) spectrometers which use crystal monochromators and analysers to determine the incident and scattered neutron energies. TAS spectrometers are mainly used to study single crystal samples, focusing on specific regions of interest in reciprocal space. The TAS instruments are optmised for different kinds of scientific studies, which depends for example on the energy and flux of the incident neutron beam, polarized neutron capability and the availability of specific sample environments.
An overview of instrument parameters is provided in the table below to help you choose the most suitable instrument. By clicking on the instrument, you can go directly to the dedicated instrument pages where more information can be found, including scientific highlights and contact details for the instrument scientists.
Triple axis instrument parameters
| Instrument | ThALES | IN8 | |||||
|---|---|---|---|---|---|---|---|
| Monochromator | PG002 | Si111 | Heusler | PG002 | Cu200 | Si111 | Si311 |
| Incident wave-number (Å-1) | 2.8, | 2.8, 1.5, 1.2 | 2, 1.5 | 4.1 | 5 | 4.1 | |
| Incident flux (n/cm2/s) | 2.4*108, 1.2*108, 5*107 | 1.3*108, 4*107, 3*107 | 2.7*107, 2*107 | 109 | 5*108 | 5*108 | 2.5*108 |
| Energy resolution (meV) | 0.8, | 0.8, | 0.4, | 1.1 | 0.9 PG002 analyser, kf = 2.662 Å-1 0.55 (Cu200 analyser, kf = 2.662 Å-1) | 1.0 | 2.2 |
| Angular range (°) | 120 | 120 | 120 | 120 | 120 | 120 | 120 |
| Comments | - FlatCone - Velocity selector -High magnetic fields | FlatCone - High magnetic fields
| Polarised neutrons | FlatCone | FlatCone | ||
| Instrument | IN12 | IN20 | IN22 | ||||
|---|---|---|---|---|---|---|---|
| Monochromator | PG002 | PG002 + Polariser | Heusler (Cu2MnAl)111 | Si111 | PG002 | Heusler111 | Cu111 |
| Incident wave-number (Å-1) | 2.8, 2, 1 | 2.8, 2, 1 | 4.5 | 4.5 | 1.55, 2.662, 4.15, 6.0 | 1.55, 2.662, 4.15, 6.0 | 2.662, 4.15, 6.0, 7.4 |
| Incident flux (n/cm2/s) | 8.107, 108, 2.107 | 2.8.107, 3.5.107, 6.106 | 108 | 2*108 | 6.0x106, 27x106, 58x106, 25x106 | 1.3x106, 6.0x106, 13x106, 5.0x106 | 9.0x106, 19x106, 16x106, 2.8x106 |
| Energy resolution (meV) | 1, 0.4, 0.04 | 1, | 3 to 10% (incident energy) | 3 to 10% (incident energy) | 0.25, | 0.25, | |
| Angular range (°) | 120 | 120 | 120 | 120 | 120 | 120 | 120 |
| Comments | Velocity selector High magnetic fields | Velocity selector Polarised neutrons CRYOPAD High magnetic field for 1/2pol | Polarised neutrons Cryopad FlatCone PASTIS | FlatCone High Magnetic Fields | High magnetic fields 40T option | Neutrons Spin echo option (ZETA) | High magnetic fields |
Neutron backscattering
Neutron backscattering provides higher energy resolution than TOF or TAS by using crystal analysers that operate in a backscattering geometry. There are 2 dedicated spectrometers which differ essentially in terms of the energy of the incident neutrons and thus the energy resolution and momentum transfer. IN16b is a very versatile instrument which includes a time-of-flight option to significantly increase the dynamic range.
An overview of instrument parameters is provided in the table below to help you choose the most suitable instrument. By clicking on the instrument, you can go directly to the dedicated instrument pages where more information can be found, including scientific highlights and contact details for the instrument scientists.
Backscattering instrument parameters
Neutron spin-echo
Spin Echo Spectroscopy (NSE) achieves very high energy resolution using the change in polarization between the incident and scattered neutron beams to measure small energy changes due to the dynamics in the sample. The energy resolution is better than that of neutron backscattering and is expressed in Fourier times since the technique measures directly the intermediate scattering function I(Q,t). There are 2 dedicated spectrometers which differ essentially in terms of the detector coverage and therefore the count rate. IN15 holds the record for measuring the longest Fourier time – about 1 microsecond.
An overview of instrument parameters is provided in the table below to help you choose the most suitable instrument. By clicking on the instrument, you can go directly to the dedicated instrument pages where more information can be found, including scientific highlights and contact details for the instrument scientists.